1. Field of the Invention
The present invention relates to an apparatus for embedding information in a digital image in the form of a digital watermark or the like and reproducing the embedded information, a method for controlling the apparatus, and a storage medium.
2. Description of the Related Art
Recently, in accordance with rapid development and diffusion of computers and computer networks, various types of information, such as character data, image data, sound data and the like, are digitized.
Digital information is not degraded, for example, with the lapse of time, can always be preserved in a complete state, can easily be copied using a computer, and can easily be distributed via a network. However, such convenient properties make it difficult to assure the security of digital information.
A digital watermark is one security technique of digital information. According to this technique, by embedding the name of the owner of a copyright, the ID of a vender and other similar identification information by processing digital image data, sound data, character data and the like so as not to be perceptible by a human being, illegal copying can be traced.
Accordingly, the digital watermark also has the features that main data and subdata embedded therein is difficult to separate, and therefore can always be recognized and used as single data.
Recently, in medical fields, management of patient information in which various sets of information are efficiently linked by digitizing medical records and diagnostic images and utilizing a computer is in progress. In such fields, there is a request to inseparably hold digital medical data, such as digital X-ray images and the like, and additional information thereof (such as patient/diagnosis information).
Providing digital medical data and additional information thereof (such as patient/diagnosis information) in an inseparable state has the following two advantages.
The first advantage is that it is unnecessary to separately manage the above-described two types of information. The second advantage is that by holding information for identifying a patient in a state of being inseparable from digital medical information, the digital medical information can be used as evidence.
Conventionally, after embedding subdata by slightly changing main data using the digital watermark technique, the subdata is detected/extracted from the main data after the change. At that time, it is difficult to restore the main data before the change.
It is unsuitable to apply the above-described conventional technique to actual medical fields in which, for example, main data is sometimes a diagnostic image of a patient, because examination of data changed from the original main data may result in an inaccurate diagnosis.
Accordingly, it is necessary at the time of diagnosis to restore digital medical data which is not degraded.
In medical fields, a clear indication of a region of interest in main data (image) is sometimes used as reference information at a diagnosis or reference information for other functions. This information indicating the region of interest desirably belongs to the main data (image). If such data is present as data separate from the main data, the information indicating the region of interest can be easily changed by anybody, whereby an appropriate diagnosis may not be performed.